Sodium reabsorption in the DCT and in the cortical portion of the collecting system is accelerated by the secretion of
(a) ADH
(b) Renin
(c) Aldosterone
(d) Erythropoietin

Verified step by step guidance

Step 1: Understand the role of each hormone listed in the options in relation to kidney function and sodium reabsorption.

Step 2: Recall that ADH (antidiuretic hormone) primarily increases water reabsorption in the collecting ducts but does not directly increase sodium reabsorption.

Step 3: Recognize that Renin is an enzyme secreted by the kidneys that initiates the renin-angiotensin-aldosterone system but does not directly cause sodium reabsorption.

Step 4: Identify Aldosterone as a hormone secreted by the adrenal cortex that acts on the distal convoluted tubule (DCT) and cortical collecting duct to increase sodium reabsorption by stimulating sodium channels and sodium-potassium pumps.

Step 5: Note that Erythropoietin primarily stimulates red blood cell production and does not influence sodium reabsorption in the kidney.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Sodium Reabsorption in the Distal Convoluted Tubule (DCT)

The distal convoluted tubule (DCT) is a segment of the nephron where sodium ions are actively reabsorbed from the filtrate back into the bloodstream. This process is crucial for maintaining electrolyte balance and blood pressure. Sodium reabsorption here is regulated by hormones that influence transporter activity.

Role of Aldosterone in Sodium Reabsorption

Aldosterone is a steroid hormone secreted by the adrenal cortex that increases sodium reabsorption in the DCT and cortical collecting duct. It promotes the synthesis of sodium channels and Na+/K+ ATPase pumps, enhancing sodium uptake and potassium excretion, which helps regulate blood volume and pressure.

Functions of ADH, Renin, and Erythropoietin

ADH primarily regulates water reabsorption in the collecting ducts, renin initiates the renin-angiotensin system affecting blood pressure, and erythropoietin stimulates red blood cell production. None of these directly accelerate sodium reabsorption in the DCT or cortical collecting system like aldosterone does.

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